Safety locking tool holder for pneumatic hammer

ABSTRACT

A safety locking holder for mounting an attachment tool onto a pneumatic hammer prevents tool removal when the holder is fully screwed onto the hammer. The holder includes a slotted end portion and an open chamber portion which permit ready insertion and removal of an attachment tool when the holder is in nonlocking engagement with the hammer.

United- States Patent [72] Inventor James 0. Taylor [56] References Cited Lantana, Fla. UNITED STATES PATENTS pp 745,050 1,731,836 10/1929 Williams 279/19x iii} fillffmed $312133? FOREIGN PATENTS a [73] Assignee Florida Pneumatic Manufacturing 713,196 1954 England 279/19 Corporation Primary ExaminerAndrew R. J uhasz Lanlalla, Assistant ExaminerDonald D. Evenson Continuation-impart 0fapplication Attorney-Larson, Taylor and Hinds 710,235, Mar. 4, 1968.

[54] HOLDER FOR ABSTRACT: A safety locking holder for mounting an at- 6 Cl 8 D tachment tool onto a pneumatic hammer prevents tool "wing removal when the holder is fully screwed onto the hammer. [52] U.S.Cl 279/19 The holder includes a slotted end portion and an open [5 1] Int. Cl B23b 31/06 chamber portion which permit ready insertion and removal of [50] Field of Search 279/19, an attachment tool when the holder is in nonlocking engagel9.6, 19.7 ment with the hammer.

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INVENTOR JAMES o. TAYLOR o z 3.07/9? ATTORNEYS SAFETY LOCKING TOOL HOLDER FOR PNEUMATIC HAMMER CROSS REFERENCE TO RELATED APPLICATION The present application is a continuation-in-part of US. application Ser. No. 710,235 filed Mar. 4, 1968.

FIELD OF THE INVENTION The present invention generally relates to pneumatic hammers and more particularly to safety locking means for attachment tools adapted to be mounted onto pneumatic hammers.

THE PRIOR ART Pneumatic hammers impart a rapid reciprocatory movement to an attachment tool through the impact of a pneumatically operated reciprocating piston located within the hammer against the shank end of the tool. Many different types of attachment tools may be utilized and thus'it is necessary to provide the hammer with means for mounting these tools which permits easy removal thereof so that one tool may be readily substituted for another.

In accordance with one such prior art tool holder a rigid coil spring adapted to be threadably received on the end of the hammer includes an outwardly extending portion thereof for supporting the tool. The support portion of the holder is formed substantially in the shape of an inverted U such that the tool body rests in the yoke of the U and a conventional flange formed between the shank' and the tool body abuts against the U-shaped portion during operation. The holder support thus forms both a support for the tool as well as a limit stop for restricting the axial movement of the tool after impact with the hammer piston. The support portion of the holder is spaced from the body portion formed by the coils and this arrangement together with the U-shaped portion permits ready substitution of one tool for another without necessitating the unscrewing of the holder from the end of the hammer.

Although the holder described above provides easy tool replacement and generally effective support the holder suffers one major disadvantage, namely, that the tool may be separated from the holder under working conditions. The support provided by the holder permits, some lateral movement of the tool away from the yoke of the support portion and thus under certain circumstances such as where the hammer is held at an extreme angle against the work the tool may slip out of the holder and, under the force supplied by the hammer, cause damage or serious injury.

Attempts have been made to provide a holder which locks the tool into position to thus prevent the tool from flying off the hammer during operation thereof. In one such arrangement a holder is constructed from three separate elements ineluding a solid body member having a threaded bore therethrough adapted to be received on the end of a hammer. The holder further includes a two-piece generally cylindrical tool support formed by a pair of substantially identical members which when fitted together form'an externally threaded end portion adapted to be received in the bore of the body member. The assembled tool support members also form a central bore for supporting the body portion of a chosen tool as well as a chamber communicating with the bore which determines the limits of motion of the tool. To replace one tool with another the two-piece support must be unscrewed from the body member, the tool removed from between the support members, the new tool placed between the members and the members fitted together therearound, and the reassembled support screwed back into the bore of the body member. It will be appreciated that this process is tedious particularly where it is necessary to replace tools with any frequency. Further, the fact that a three-piece construction is necessary increases the cost of manufacture and handling as well as the possibility of losing or misplaeing any of the holder components. Thus it will be appreciated that although the arrangement described does provide generally effective locking of the tool within the holder it does so at the expense of a sig- SUMMARY OF THE INVENTION In accordance with the present invention there is provided a mounting device of the type described which enables easy mounting and removal of a pneumatic hammer attachment tool while providing effective locking of the attachment tool to prevent the tool from separating from the hammer and thus causing possible personal injury and/or physical damage. In accordance with the invention a mounting device or holder is provided wherein tightening" of the engagement of the mounting device beyond a predetermined point prevents removal of the attachment tool from the holder and thus provides a safety lock for the tool. Prior to. this tightening the tool may be readily inserted into and removed from the holder.

In accordance with a presently preferred embodiment the mounting device of the invention is of unitary construction and includes a bodyportion adapted to be mounted on a pneumatic hammer and a slotted end portion for supporting the body of an attachment tool. The end portion and body portion are interconnected by intermediate portion which is formed to define an open chamber permitting reciprocating axial movement of the tool. This chamber communicates with a threaded bore in the body portion which serves in mounting the tool holder onto the pneumatic hammer.

In operation the attachment tool is disposed with the holder such that the body portion of the tool rests in the slot in the .end portion of the holder, and the flange and the shank of the tool lie within the chamber and communicating bore. The shank extends into a bore in the hammer so that the end thereof may be contacted by the operating piston of the hammer during hammer operation. The holder is dimensioned relative to the length of the shank of the attachment such that the holder body may be securely threaded onto the hammer, i.e., with the end of the hammer extending a substantial distance into the bore thereof, without impairing the ready insertion and removal features of the holder. Thus the holder need not be removed from the hammer when tool replacement or substitution is desired. However, in accordance with an important feature of the invention, when the holder body is threaded onto the hammer beyond a point corresponding to a predetermined depth of extent of the end portion of the hammer into the bore of the body of the tool the tool is fixedly captured within the holder and the bore of the-end portion of the hammer and cannot be removed. The difference between the locking and nonloeking positions of the holder body may conveniently be made one turn. Thus locking and unlocking of the tool onto the hammer is effected through a simple rotative manipulation of the body portion of the holder.

In accordance with a further feature of the present invention a biasing spring disposed within the holder chamber bears against the flange of the attachment tool and the face of the end portion of the hammer. This arrangement prevents contact of the end of the shank of the tool with the operating piston of the hammer except where the tool is pressed against the work and the biasing force of the spring is overcome.

BRIEF DESCRIPTION OF THE DRAWING Other features and advantages of the invention will become apparent upon consideration of the following description taken together with the accompanying drawings wherein:

FIG. 1 is a side elevation view of a, pneumatic hammer in corporating a holder in accordance with a first embodiment of the invention;

FIGS. 2 and 3 are end and side elevation views, respectively, of a prior art holder;

FIG. 4 is an enlarged sectional side elevation view corresponding to FIG. 1 showing the cooperation between the tool, holder and hammer;

FIG. 5 is a perspective view of the holder of FIGS. 1 and 4;

FIG. 6 is a view similar to FIG. 1 of a presently preferred embodiment of the invention but with only the end portion of the hammer shown;

FIG. 7 is an enlarged sectional side elevation view of the holder of FIG. 6, similar to FIG. 4; and

FIG. 8 is a perspective view of the holder of FIGS. 6 and 7, similar to FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows the safety holder in accordance with a first embodiment of the invention mounted on an exemplary hammer generally denoted H. The hammer H includes a cylindrical body section 10 having a handle member 12 depending downwardly therefrom and a barrel member 14 projecting outwardly therefrom. Extending outwardly of the handle 12 is a manually operable air pressure control device 16. A flexible line 18 depending from handle 12 connects the hammer H to a suitable source of compressed air. The hammer H includes an operating mechanism (not shown) for automatically reciprocating a piston 19 (FIG. 4), in a conventional manner. It will be understood that the particular details of the operating mechanism form no part of the present invention and pneumatic hammers other than that illustrated may be utilized. Reference may be made, for example, to U.S. Pat. No. 2,655,901 for the details of construction of a suitable operating mechanism.

The novel tool mounting device or holder of the present invention generally denoted 20 is threadably engaged with barre] 14 of hammer H. Holder 20 mounts a suitable attachment tool 22 onto barrel 14 in a manner described hereinbelow. While a great number of different tools corresponding to tool 22 may be mounted on hammer 20 (tool 22 may for example be a chisel) these tools characteristically comprise, as may best be seen in FIG. 4, a shank 24, anintermediate annular flange 26 and a body portion 28 which includes the working portion (not shown) of the tool.

In order to provide a background for understanding the present invention a prior art attachment tool holder will be considered. Referring to FIGS. 2 and 3, there is shown a holder 30 comprising a rigid spring member which includes a tightly coiled body portion 32 adapted to mount the holder 30 onto a hammer and a spaced generally U-shaped support or collar portion 34. The coils 36 of body portion 32 are adapted to be threadably received in grooves formed in the barrel of a pneumatic hammer (not shown). The body portion 28 of a tool 22' shown in phantom in FIGS. 2 and 3 rests in the yoke of U-shaped support portion 34 while a flange portion 26 abuts against the inner surface thereof as shown, the inner surface of support portion 34 serving as a limit stop for axial travel of the tool 22. The shank 24' of the tool 22' extends into a longitudinal bore (not shown) in the hammer.

Tool 22' may be removed from holder 30 by lifting the body portion 24 out of U-shaped support 34 while simultaneously withdrawing the shank 24 from the bore in the barrel of the hammer. As discussed hereinabove although the holder arrangement of FIGS. 2 and 3 provides for ready insertion and removal of an attachment tool with this arrangement the tool is not prevented from separating from the holder under all circumstances. The forces described above which are exerted by a user in attempting to remove the tool from the holder may be reproduced during operation of the hammer under certain circumstances, thus causing separation of the tool and holder. An example of one such circumstance is where the tool is used such that the body portion thereof forms a small angle with the surface of the work so that significant pivoting of the tool takes place. If at this time the tool slides off the end of the work it may separate from the holder and fly off of the hammer. I

Referring again to FIG. I and particularly to FIGS. 4 and 5 a holder 20 in accordance with the invention is shown. The holder 20 generally comprises a cylindrical body portion 40, an intermediate half cylinder 42 which includes a longitudinal chamber 44, and a collar portion 46.

Body portion 40 includes a central bore 50 (FIG. 4) therethrough which is threaded as indicated at 52 to permit threadable engagement of the holder 20 with an externally threaded end portion 54 of barrel 14 (see FIG. 4). Body portion 40 includes an outer lip 40a which limits the extent of travel of body 40 on end portion 54. Bore 50 communicates with a bore 540 formed in end portion 54 adapted to receive shank 24 of tool 22. Movement of shank 24 to the right as shown in FIG. 4 is limited by the abutment of an enlarged bellshaped portion 24a thereof adjacent flange 26 with the portion of end portion 54 which defines the opening of bore 54a. As is shown in FIG. 4 bore 54a includes a corresponding bellshaped portion 54b at the opening thereof which mates with bell-shaped portion 24a to provide a snug fitting of tool 22 into bore 540. Shank 24 in the extreme rightward position thereof extends well into piston chamber 19a thus enabling piston 19 to make solid impact therewith.

Collar 46 is of generally flat disclike construction and includes a generally U-shaped slot or recess 56 bounded on opposite sides by pronglike members 58 and 60 and adapted to receive and serve as a rest for the body portion 28 of tool 22.

Chamber 44 formed in intermediate portion 42 of the holder 20 is generally semicircular in cross section and communicates with bore 50 and slot 56. The diameter of chamber 44 is such as to permit unimpeded axial travel of tool 22 therealong. Chamber-forming portion 42 includes a tapered stop portion 42a adjacent collar 46 which serves as abutment to limit the travel of tool 22. Thus with tool 22 mounted as shown in FIG. 4, tool 22 may move, under the impact provided by operating piston I9, between the point at which the bore-defining portion of end portion 54 of barrel l4 abuts with the enlarged portion 24a of shank 24 and the point at which the distal face of flange 26 abuts with stop portion 42a im mediately adjacent collar 46.

A spring 62 (FIG. 4) prevents contact between shank 24 and piston 19 when the tool is not in use. Spring 62 is disposed between flange 26 of tool 22 and the face ofend portion 54 of hammer H and includes a first loop 64 which surrounds and bears against portion 24a and a second loop 66 which bears against the end face of end portion 54. Spring 62 prevents, in the absence of other forces, movement of tool 22 (to the right as shown in FIG. 4) sufficient to permit contacting of shank 24 by piston 19. Spring 62 thus prevents injury or damage which might occur by inadvertent energization of the hammer. It will be understood that the biasing force furnished by spring 62 is relatively weak and is easily overcome by the pressing of the tool against the work. It will be further appreciated that under working conditions the tool is returned by rebounding against the work to a position where it receives the next blow from the piston and thus even in the absence of spring 62 inadvertent operation of the hammer H will result in a single leftward movement of the tool 22.

As will be described in detail hereinbelow the axial position of holder 20 along end portion 54a will determine whether or not the mounted tool 22 may be removed. Preferably, with the holder 20 fully screwed onto the hammer H the holder 20 is in a locking position whereas with the holder 20 less than fully screwed on, e.g., with the holder unscrewed by one turn or more from the fully screwed-on position, the holder is in a nonlocking position.

In operation, with the holder 20 in the nonlocking position thereof the tool 22 may be freely inserted into the holder by inserting the end of shank 24 into bore 54a and lowering body portion 28 into slot 56. It will be appreciated that as tool 22 is lowered into slot 56 the extent to which the shank 24 may be entered into bore 54a is increased and that with tool 22 parallel to the longitudinal axis of holder 20 the tool 22 is freely movable axially in the holder. In a similar manner tool 22 may be readily removed from the holder 20 by sliding the tool axially away from the hammer barrel I4 and then lifting the tool body 28 out of slot 56. The positions of tool 22 and holder 20 before removal of the tool 22 are indicated in phantom in FIG. 4. Lifting of the tool 22 out of the slot 56 causes flange 26 to clear stop portion 42a which permits further slight axial movement of the tool 24 away from barrel l4 and thus permits final removal of the tool 22. The clearance between shank 24 and the bore 54a is such as to permit some pivoting of the upper surface of the end of shank 24 about the edge of end portion 54 fonning the opening of bore 54a. This pivoting action enables the lower edge of shank 24 to clear bore 54a.

With holder in the locking position thereof the entire holder including collar portion 46 is moved closer to barrel l4 and thus even with movement of tool 22 to the furthest leftward position thereof as viewed inYFlG. 4 the distance that shank 24 extends into bore 54a is such as to prevent sufficient pivoting of tool 22 to enable removal of the tool. In this position the pivot point about which the upper surface of shank 24 pivots is further from the end of shank 24 and the lower edge portion of shank 24 cannot clear the bore 54a. It is noted that I the distance which dictates whether or not the tool 22 may be removed from the holder is that between the point where the distal face of the flange 26 contacts the stop portion 42a adjacent collar 46 and the point where the bell-shaped portion 54b of bore 54a begins. This latter point is critical, rather than the opening of bore 540, because bell-shaped portion 54b permits relatively free pivoting of the end of shank 24. The clearance between the shank diameter and the bore diameter is also critical but is a predetermined and generally standard quantity.

To provide a specific example it is noted that for a standard tool having a shank corresponding to shank 24 measuring approximately 1 2/3 inches from the distal surface of flange 26 to the end surface of the shank the critical distance described hereinabove, that is, the distance between the abutment point of flange 26 and stop 42a and the beginning of bell-shaped portion 54b, is approximately I Arinches. Thus, generally,

where the distance between the abutment point of the flange 26 and stop 42a and the beginning of bell-shaped portion 54b is greater than this value the tool may be removed from the holder whereas where this distance isless than this value the tool cannot be removed. In actual practice the difference between the locking and unlockingpositions of the holder may be made to correspond to the travel of the holder upon one complete turn of the holder body 40 on end portion 54, this difference corresponding to the distance between a position where the tool is securely locked and one where the tool is relatively easily removed.

Referring to FIGS. 6 to 8, a presently preferred embodiment of the holder of the present invention is shown. The holder, which is generally designated70, may be conveniently considered as comprising a body portion 72 an open chamber portion 74 and an end portion 7 I Body portion 72 is generally cylindrical in shape and is adapted through internal threading 78 to receive the threaded end portion 54' of the barrel 14" of ahammer H similar to hammer H of FIG. .1. Threading 78 extends for approximately two thirds of the length of the interior surface of body portion 72, the remaining third of the interior surface 80 being smooth walled and of reduced cross section. The diameter of the reduced cross section portion 80 is equal to the internal diameter of open chamber portion 74 so that a continuous smooth-walled chamber 82 is formed.

The beginning edge of the reduced cross section portion 80 forms an abutment 84 against which one turn of a spring 86 bears. Spring 86 is similar to and serves the same purpose as spring 62 of FIG. 4. Spring 86 is held in position by a steel washer 88 and a resilient O-ring which contacts the end surface of the end portions 54' of hammer H' as shown in FIG. 7. Spring 86, washer 88 and O-ring 90 are inserted into the threaded end of body portion 72 before the holder 70 is screwed onto hammer H, washer 88 and O-ring 90 cooperating with abutment 84 to provide a simple and effective means for supporting spring 86 in operating position within the holder 70. This arrangement provides rapid and sure placement of the spring 86 within the holder 70.

The open chamber portion 74 of holder 70 may be formed by the removal of an arcuate section of the cylinder wall form ing body portion 72, removal of this section exposing the bore through holder 70. The chamber defining walls 92 of open chamber portion 74 are arcuate in cross section, the length of the are formed thereby being greater than one-half of the circumference of a completed circle of that diameter. The heightened portion of the chamber-defining walls 92 serve in effecting holding of a tool 22" within chamber 82 and thus eliminate the need for the prong members 58, 60 of the embodiment of FIGS. 1, 4 and 5. As can best be seen in FIG. 8 the curved portions of walls 92 and the end portion 76 of holder 70 terminate in first and second continuous flat surfaces 94, 96 lying on opposite sides of the open chamber 74 and a bore or slot described hereinbelow.

The end portion 76 of holder 70 includes a transitional section 98 which tapers from a diameter equal to the internal diameter of continuous chamber 82 to the reduced slot 100 formed in the distal end of holder 70 concentric with chamber 82. The diameter of bore 100 is slightly larger than the body portion of the standard tool 22" as can best be seen in FIG. 6. The bore 100 is less than a full circle in cross section, the depth thereof as measured from upper flat surfaces 94, 96 being slightly less than the diameter of the body portion 28" oftool22.

Flange 26" of tool 22" is free to move within continuous chamber 82 under the. impact of a piston 19' of hammer H. The tool 22" as shown in the rest, position thereof in solid lines in FIG. 7 whereas the position thereof just prior to removal is indicated in dashed lines. The rest position of tool 22" which is determined by spring 86 is such that the shank 28" of tool 22" is spaced from piston 19 as shown.

Removal of tool 22" takes place as described hereinabove in connection with the embodiment of FIGS. 1, 4 and 5, with locking of tool 22" being effected through the screwing of holder 70 onto end member 54 whereby and member 54' extends therein a predetermined amount, and unlocking of tool '22" being effected through the unscrewing of holder 70 a predetermined amount, preferably one turn. Tool 22" pivots about the end opening of a bore 54a. in end portion 54' of hammer H and the edge of flange 26" rides up the surface of transition section 98 until tool 22 may be lifted from slot 100 and completely withdrawn from holder 70.

Holder 70 is preferably constructed of a lightweight metal such as aluminum. This construction combats any unbalance of the hammer I-I' caused by the mounting ofholder 70 on barrel 14'. Further in this regard, the reduction in length of the holder 70, occasioned by the recessing of a portion of chamber 82 within body portion 72, as compared with the holder 40 of FIGS. 1, 4 and 5 additionally aids in combatting unbalance of this type as well as provides a corresponding reduction in material necessary for manufacture. It will be appreciated, as suggested hereinbefore, manufacture of the holder of the embodiment of FIGS. 6 to 8 is generally simplified as compared with the embodiment of FIGS. 1, 4 and 5. The outer surface of holder 70 is knurled as indicated. at 102 to provide each of handling.

It will be appreciated from the foregoing that the holder of the invention provides simple yet effective means for locking an attachment tool onto a pneumatic hammer without sacrificing of the ready insertion or removal features of the nonlocking prior art holder devices. Further, the rugged unitary construction of the holder of the invention is obviously advantageous as compared with the multipiece locking holder described hereinbefore.

It will be further understood by those skilled in the art that the embodiment of the invention shown and described herein is subject to modification without departing from the scope and spirit of the invention. Accordingly, it should be understood that the invention is not limited by the exemplary embodiment shown and described but rather only by the subjoined claims. I i

lclaim: I

l. A tool mounting device for mounting a flanged attachment tool, having a body and a shank, onto a pneumatic hammer of the type which imparts a reciprocating movement to the attachment tool, said device comprising a unitary member constructed of lightweight metal and comprising a cylindrical portion including a cylindrical bore of a predetermined diameter therein having a threaded portion for engaging an externally threaded end member of a pneumatic hammer and an unthreaded portion which forms a first, closed portion of a chamber for permitting axial movement of the attachment tool; a part-cylindrical end portion which is substantially C-shaped in cross section and which defines a slot for supporting the attaching tool, said slot being of substantially circular cross section apart from an open portion thereof which permits receipt of the body of the attachment tool; and a part-cylindrical intermediate portion formed integrally with said body portion and said end portion, said intermediate portion being substantially C-shaped in cross section and defining a further, partially open portion of said chamber, the radius of said partially open portion of said chamber being equal to the radiusof said bore and being greater than the radius of said slot, the radius of said cylindrical external surface of the body portion being equal to the radius of the external surface of said end portion and to the radius of the external surface of said intermediate portion so that said unitary member includes a continuous cylindrical external surface, and the circumference of the external surface of said end portion being greater than a semicircle of the same radius and equal to the circumference of said intermediate portion so that the end surfaces of said C-shaped end portion are coextensive with the end surfaces of said C-shaped intermediate portion, the end surfaces of said end portion comprising first and second generally flat surfaces and the end surfaces of said intermediate portion comprising first and second generally flat surfaces, the first surface of said end portion forming a continuous surface with the first surface of said intermediate portion and the second surface of said end portion forming a continuous surface with the second surface of said intermediate portion, the length of said chamber defined by said closed and partially opened portions, and the diameter of said bore, relative to the length and diameter of the attachment tool being such that tightening of the engagement of said threaded cylindrical portion beyond a predetermined position along the extent of the end member of the pneumatic hammer prevents removal of the attachment tool from the mounting device and such that the attachment tool can be inserted into the mounting device and removed therefrom without necessitating removal of the mounting device from the pneumatic hammer.

2. A tool mounting device as claimed in claim 1 wherein said end portion includes a transitional section located between said slot and said further partially open portion of said chamber, and of longitudinal cross section tapering from the relatively large radius of said chamber to the relatively small radius of said slot.

3. A tool mounting device as claimed in claim 1 wherein one unlocking turn of said device is sufficient to permit removal of the attachment tool.

4. A tool mounting device as claimed in claim 1 further comprising a coil spring located within said chamber for resiliently positioning an attachment tool within said chamber, said coil spring including a first coil located at one end thereof for engaging the shank of the attachment tool and a second coil located at the other end thereof for abutting with a surface of the internal wall of said body portion.

5. A tool mounting device as claimed in claim 4 wherein the radius of said threaded portion of said bore is greater than the radius of said unthreaded portion of said bore and said abutting surface is located between said threaded and unthreaded portions of said bore and extends transversely thereto, said device further comprising washer and O-ring means positioned between the end member of the hammer and said second coil for positioning said coil spring within said chamber, the radius of said second coil being greater than the radius of said first coil. D

6. A tool mounting device as claimed ll'l claim 1 wherein the external surface of said unitary member is knurled over the entire extent thereof to permit easy handling of said unitary member. 

1. A tool mounting device for mounting a flanged attachment tool, having a body and a shank, onto a pneumatic hammer of the type which imparts a reciprocating movement to the attachment tool, said device comprising a unitary member constructed of lightweight metal and comprising a cylindrical portion including a cylindrical bore of a predetermined diameter therein having a threaded portion for engaging an externally threaded end member of a pneumatic hammer and an unthreaded portion which forms a first, closed portion of a chamber for permitting axial movement of the attachment tool; a part-cylindrical end portion which is substantially C-shaped in cross section and which defines a slot for supporting the attaching tool, said slot being of substantially circular cross section apart from an open portion thereof which permits receipt of the body of the attachment tool; and a part-cylindrical intermediate portion formed integrally with said body portion and said end portion, said intermediate portion being substantially C-shaped in cross section and defining a further, partially open portion of said chamber, the radius of said partially open portion of said chamber being equal to the radius of said bore and being greater than the radius of said slot, the radius of said cylindrical external surface of the body portion being equal to the radius of the external surface of said end portion and to the radius of the external surface of said intermediate portion so that said unitary member includes a continuous cylindrical external surface, and the circumference of the external surface of said end portion being greater than a semicircle of the same radius and equal to the circumference of said intermediate portion so that the end surfaces of said Cshaped end portion are coextensive with the end surfaces of said C-shaped intermediate portion, the end surfaces of said end portion comprising first and second generally flat surfaces and the end surfaces of said intermediate portion comprising first and second generally flat surfaces, the first surface oF said end portion forming a continuous surface with the first surface of said intermediate portion and the second surface of said end portion forming a continuous surface with the second surface of said intermediate portion, the length of said chamber defined by said closed and partially opened portions, and the diameter of said bore, relative to the length and diameter of the attachment tool being such that tightening of the engagement of said threaded cylindrical portion beyond a predetermined position along the extent of the end member of the pneumatic hammer prevents removal of the attachment tool from the mounting device and such that the attachment tool can be inserted into the mounting device and removed therefrom without necessitating removal of the mounting device from the pneumatic hammer.
 2. A tool mounting device as claimed in claim 1 wherein said end portion includes a transitional section located between said slot and said further partially open portion of said chamber, and of longitudinal cross section tapering from the relatively large radius of said chamber to the relatively small radius of said slot.
 3. A tool mounting device as claimed in claim 1 wherein one unlocking turn of said device is sufficient to permit removal of the attachment tool.
 4. A tool mounting device as claimed in claim 1 further comprising a coil spring located within said chamber for resiliently positioning an attachment tool within said chamber, said coil spring including a first coil located at one end thereof for engaging the shank of the attachment tool and a second coil located at the other end thereof for abutting with a surface of the internal wall of said body portion.
 5. A tool mounting device as claimed in claim 4 wherein the radius of said threaded portion of said bore is greater than the radius of said unthreaded portion of said bore and said abutting surface is located between said threaded and unthreaded portions of said bore and extends transversely thereto, said device further comprising washer and O-ring means positioned between the end member of the hammer and said second coil for positioning said coil spring within said chamber, the radius of said second coil being greater than the radius of said first coil.
 6. A tool mounting device as claimed in claim 1 wherein the external surface of said unitary member is knurled over the entire extent thereof to permit easy handling of said unitary member. 